Sound reproducing and recording device



June 24, 1930 J. T. SERDUKE SOUND REPRODUCING AND RECORDING DEVICE Filed Jan. 22, 1929 Inventor James T. Serduke,

by His Attorney.

STATES JAMES '1. SERDUKE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL'ELECTRIC PATENT OFFICE COMPANY, A CORPORATION OF NEW YORK SOUND REPRODUCING AND RECORDING DEVICE Application filed January 22, 1929. Serial No. 834,250.

My invention relates to apparatus for re producing or recording sound, and has for ts principal object the provision of an improved apparatus capable of faithfully responding to electric impulses dependent on sound.

Various devices for the reproduction or recording of sound, operated'by electric impulses, have been provided in the past. Many of these devices include an armature or coil mounted to move in a magnetic field and connected to a diaphragm or recording stylus. Such devices have the disadvantage that they are complicated, require accurate workmanship, and are expensive.

In accordance with my invention these difliculties are minimized by providing, for such devices, a movable member or members composed of a material whose physical d1- mensions vary in response to variations in a magnetic field acting thereon, and arranging such member or members to operate a sounding diaphragm or a recording stylus.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 1llustrates a loud speaker embod ing my invention in its simplest form; Flg. 2 1s a modification thereof; and Fig. 3 illustrates a phonograph record cutter embodylng my 1nvention.

1 illustrates a loud speaker including a rigld conical diaphragm 10 WhlCll maybe supported by" a flexible annulus-surrounding its base and a coil 11 adapted toreceive the electric impulses which are to be converted into sound. The coil 11 is arranged to create a magnetic field which acts upon a driving member 12. Member 12 is placed through the center of the coil 11, is rigidly mounted at one end to abase'l3 and at the other end is attached to the cone 10.-

The member 12 may be either a rod or tube which is capable of varying its length 1n response to variations in the magnetlc field created bycurrents in the C011 11. In the investigations ofthe magneto-strictlon charsome metals elongate with an increase of intensity of a magnetic fieldracting thereon and others decrease in length with the same increase in intensity. The theory of such expansion or contraction is not clearly understood but has been proven to exist. In my investigations I have found for instance, that alloys comprising between 40% and 70% cobalt alloyed with either iron or nickel, expand as much as .00084 millimeter per centimeter of length for an increase of 100 to 200 gausses in intensity of the magnetic field. Nickel on the other hand contracts approximately the same amount for the same increase in magnetic intensity. This contraction and expansion varies with difl'erent alloys and varies even with difl'erent treatments of the same alloy.

Fig. 2 illustrates a modification of the invention in which member 12 is replaced by a driving mechanism including tubes or rods 14 and 15 of which 14 elongates and 15 contracts with the same variation in the field intensity. I

Caps 16 and 17 are mounted upon the upper ends of the magneto-strictive members 14 and 15 respectively, and support a member 1'8 by means of spring members 19 and 20., The latter are spaced apart, and are rigid in a vertical plane but resilient horizontally. The opposite ends of the members 14 and 15 are imbedded in a member 25 which in turn is supported by base 13. In operation therefore, the caps 16 and 17 and therefore springs 19 and 20 move in opposite directions under the influence. of the magnetic field variations and thereby move the whereby a groove'is cut in the blank 23 which is rotated by plate 24.

'VVhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination of means for producing a magnetic field, and two members rigidly mounted at one end and respectively operable to contract and elongate when subjected to said field.

2. The combination of means for produc-' ing a magnetic field, a plurality of magnetostrictive members rigidly mounted at one end and respectively operable to contract and elongate when subjected to said field, a sound diaphragm, and driving means ar ranged between said diaphragm and said magneto-strictive members.

3. The combination of means for produc- I ing a magnetic field, a plurality of magnetostrictive members rigidly mounted at one end and respectively operable to contract and elongate when subjected to said field, a sound. diaphragm and driving means arranged between said diaphragm and the free ends of said magneto-strictive members.

4. The combination of means for producing amagnetic field, two magneto-strictive members rigidly mounted at one end and operable to oppositely vary their respective lengths when subjected to said field, a sound diaphragm, and resilient driving means arranged between said diaphragm and the free ends of said ma-gneto-strictive members.

5. The combination of means for producing a magnetic field, two magneto-strictive members each rigidly mounted at one end and respectively operable to contract and elongate when subjected to said field, and a movable member in operative relation with the other end of each of said magneto-strictive members.

6. The combination of means for producing a magnetic field, two magneto-strictive members rigidly mounted at one end and respectively operable to contract and elongate when subjected to said field, a movable member, and driving means arran ed between said movable member and t e free ends of said magneto-strictive members.

In witness whereof, I have hereunto set my hand this 21st day of January, 1929.

JAMEST. SERDUKE. 

